Posted by:
FR
at Thu Feb 12 21:27:18 2009 [ Email Message ] [ Show All Posts by FR ]
THere is a basic concept for the groups we see. The truth is, not all members of the same species do this, not even in the same colony.
For instance if you take some rattlesnakes, particularly the ones that are known to den. They stay at the den sight at least until the females cycle and copulate. Then they leave the area. Other types stay in the same area all year. And as I mentioned, at some times, they do one or the other, or both.
Our montane rattlesnakes are ones you WOULD THINK would den, but they don't, the congregate in pairs and trios and stay together year around.
At the same time, you can find pairs off by themselves, breeding. Not in dens. Also you find single males posting all over the place. Posting is staying out in the open and easy to see. We will see these same single males sitting and waiting year after year. But no females are to be had.
So the question is, why do they group up in dens or congregations, when they do not have too? Its a good question.
Well after years of watching, what we see is, the groups appear to be in a extremely reliable habitat. That is, its successful at supporting recruitment, in almost all years. So these areas become hubs. That is, during years of contraction, the population shrinks back to these areas. Then in years of heavy recruitment, they move out and use many other marginal habitats. That is, until they are re-educated. That is, harsh conditions kills them off in these marginal areas. By killing them off, the population is educated to stay where they survive.
This is very true and explainable with our desert tortoise. They congregate and live and breed, high up in rock outcrops. They climb up rock faces, etc. TORTS YOU SAY. Yup, torts. In wet times, they move down into bajadas, flatter grassy areas at the base of rocky ranges. As soon as it drys out, as in droughts, these bajadas torts die off.
Now the funny part, they protected the torts because they were all dying and none were found to be in reproductive conditions. Yup, you got it, after droughts they died off in the lower flat areas. So Game and fish states they have some Respitory infection and this disease is killing them. The truth is, they were dying from drough induced lack of an immune system. The individuals in the rocks were not only healthy, but producing babies like crazy.
The problem is, Torts are thought of as grassland reptiles. That is historically, they were. But here and now, they have moved into rocky areas because of one thing. MOISTURE. Rock beds catch and hold water, the flat lands do not. So here, these hubs can be thought of as survival points.
There are many things that can restrict habitat. One that is not thought of and may be the most important is nesting. These snakes and lizards are nesters, that is, they make or use a particular type of nest. Whats important about the nests is, they not only allow the eggs to hatch, but also support the neonates to survive.
We know rattlesnakes pick these places very consistantly. Whats interesting is, live bearers also pick similar places. hmmmmmmmmm see your right, this is fun. Cheers
[ Hide Replies ]
|
RE: I was going to say - FR, Thu Feb 12 21:27:18 2009